I. Field
The present disclosure relates generally to communication, and more specifically to techniques for generating reference signals for multiple communication systems.
II. Background
A wireless device (e.g., a cellular phone) may be designed to support multiple communication systems. These systems may have different carrier frequencies and chip rates. Each system may also have certain requirements on clock signals used for digital processing and local oscillator (LO) signals used for frequency downconversion and/or upconversion.
Separate clock and LO generation circuits may be used for each system supported by the wireless device and may be designed to meet all requirements of that system. The clock and LO generation circuits for each system may include, e.g., a voltage controlled temperature compensated crystal oscillator (VCTCXO) and one or more phase locked loops (PLLs). The VCTCXO generates a reference signal having an accurate frequency and may be locked to the carrier frequency or the chip rate of the system. The PLL(s) may be locked to the reference signal and used to generate the required clock and LO signals, which would then have the same frequency accuracy as the reference signal.
If the wireless device supports multiple systems, then multiple sets of clock and LO generation circuits may be used for these systems. These clock and LO generation circuits, although effective, increase design complexity as well as cost for the wireless device.
There is therefore a need in the art for techniques to support multiple communication systems in an efficient and cost effective manner.